Growing Up With the World's Greatest Hitman
by halcyonranhuer
Summary: It isn't just Reborn watching over Tsuna's growth. Tsuna watches his as well. Oneshot.


**So... I am stuck in R27 hell, be it parental!Reborn or lover, I am just stuck (waving my hands).**

 **I JUST THINK IT IS SO FREAKING CUTE FOR THEM TO BE TOGETHER (like the 'Canvas' song they sang together).**

 **That said.**

 **To get unstuck I have another fic! (Or more like I didn't know what do with my post exams free time so I end up writing a lot.) And then I find it in my computer haha. I have so many stray stories. I have a few here, but I am putting this one up first. I will update the rest soon, don't worry haha.**

 **This relationship here between Reborn and Tsuna may be interpreted in many ways so its up to the readers. I always wonder what would be like if Reborn grows up and plus, I want to portray their relationship growing closer to one another. That said, do enjoy. Sorry for the long A/N.**

* * *

He was fourteen.

Sometimes whenever he decided to go somewhere, Reborn would perch on his shoulder with the grace that beseeched a bird, or that he would run atop the walls with the grace that beseeched a cat. He always enjoyed moments like these with the infant hitman. Because Reborn was decent, as long as he did not pull out the Leon gun and started shooting the life out of Tsuna.

He was fifteen.

It was the one time he recalled lifting the hitman up, feeling his small body, warm and shivering. Bianchi was assigned on a mission to Italy then. He helped Reborn with almost anything, as the hitman was rendered immobile. In fact, most of the Acrobaleno were, the only exception was Lal. It was a bad side effect from their pacifers being removed, as now their infant bodies had to get used to the sudden tremendous intake of flames. Reborn had gotten it the worse, considering he was the strongest as well. It was quite shocking for Tsuna at first, but the younger was determined to care for him. He promised himself for the sake of Reborn's pride (and his as well) that he would not tell anyone about this. The only indication when Reborn was feeling better was when he shot Tsuna if he had approached the hitman too closely.

He was sixteen.

Reborn now had the body of a preschool child. Apparently Verde had mentioned that their growth rates were much faster to accommodate their large flames. However, the sudden change had Reborn occasionally stumbling with his feet. Tsuna was the only who had noticed that, seeing as he was near his tutor all the time. Sometimes if Reborn nearly tripped and fall over, to help regain his footing, Tsuna would purposely pretend to fall over as well, so it would look as if Reborn was trying to step on him. At times like this, he appreciated how he was 'dame-Tsuna'.

He was seventeen.

Reborn was now an elementary school kid. It also started the first time he went shopping with Reborn. The hitman had needed shoes, since he was growing too fast. It was not exactly memorable, in fact, most of Tsuna's experiences with the hitman involved life threatening shenanigans. Reborn kept kicking the brunette in the face, whenever Tsuna tried to kneel and help Reborn with the laces. (Reborn had issues with his motor skills because of his fast growing body and he didn't have time to adapt to it properly.)

He was eighteen.

Tsuna was shocked at their growth rates. He mentioned to Verde (when he saw him during a party) that they were growing far too quickly. Most of them looked like the end of the elementary school years and moving on to middle school. Verde said it was natural, that they were growing much faster, despite the issues with their motor skills. This time Reborn looked much more familiar to the adult he had seen four years ago during the Acrobaleno trial. Lal and Colonello collapsed in exasperation when he mentioned it to Reborn who just narrowed his eyes.

"Took you long enough, Dame-Tsuna."

He was nineteen.

Reborn looked like a middle schooler in his last year. Tsuna ignored how the hitman was catching up to his head. It was also the period where Tsuna had taken on the mantle of Vongola Decimo officially. Since after Tsuna was fourteen, there were many other various uprising criminal groups that wanted to usurp the Vongola (as crazy as it sounded, yes). There were also many other big, dangerous schemes that required the Vongola Decimo-in training to shut down, not to mention, Tsuna hadn't built his resolve until now. Still he did it, and he watch his tutor grinned with a sort of pride, before kicking him. The brunette also had realised that kicks coming from the hitman were more frequent; he'd lament about it later. For now, he would laugh whenever Reborn's voice seemed to crack.

He was twenty.

Reborn was easily Tsuna's height or taller and it irked the brunette to no end. Puberty had done its part, Tsuna did get a growth spurt, but it would never rival any of his friends. He could only pin the blame on his genes or his mother's for the matter. Reborn seemed more accustomed in this body. He no longer fumbled or tripped despite growing up fast and Tsuna had recalled that Verde said that they would get used to the growth rates after a period. He then dodged a bullet meant for his head. It had also seemed that Reborn's shooting skills had gotten much faster. Tsuna also had to admit he would not be getting used to Reborn's low tone any time soon.

He was twenty-one.

There was a big celebration on his birthday and he was surprised everyone who knew remembered it, and that it was not shared with Reborn's. He thought everyone would have forgotten after the madness that had happened on the hitman's birthday.

"We can't just leave you to the desk, Tsuna!" Yamamoto laughed. Tsuna felt a dull warmth spreading at the base of his heart, because honestly, his birthday hadn't really been that much of a deal. More than that however, his father and mother were there setting up the cakes for him, a feat that had never happened in years. And then there was Reborn who would bark about the sloppy decorations and then tilted his fedora a little in acknowledgement of his student.

Tsuna didn't need to know who called for his father.

He was twenty-two.

Reborn was now literally looming over him. Tsuna hated it, Reborn seemed to enjoy it. His tutor's presence seemed to be more and more of something bigger in his life, something indispensable, not that he would say it. Tsuna watched as how Reborn would sometimes coo over his suits, which was a rather surprising and new thing for the brunette. He knew that his tutor was a closet ardent costume collector, but not someone who actually enjoyed his suits (since the hitman wore black half the time). Now, he had a broader range of attire selection. Reborn also had gotten much faster, his breakfast-stealing skills became legendary, not that Tsuna would let him touch his (though he still lost).

He was twenty-three.

Reborn looked like his mid-twenties, exactly how he was, or a just a bit of a few years, before the Acrobaleno curse had happened. Reborn seemed to be much happier these days. Yet on some nights, Tsuna silently wondered when the hitman would pack up and leave. After all, Reborn's job was sort of accomplished. The hitman had asked to stay after Tsuna had become Vongola Decimo with the excuse of tutoring the brunette to get used to the change in environment. Four years had already passed. In fact, Reborn never stayed for that long with Dino. It was also then Tsuna knew the only thing he would never get used to is the presence without his demonic Spartan of a tutor.

He was twenty-four.

Reborn looked older than him now. The Vongola family had flourished as a vigilante group since Tsuna took over. However, it might have been all the accumulated stress from the thinking and the fighting when Tsuna fell so badly ill one autumn, to the point where he had to be in the hospital. Somehow Tsuna noticed that Reborn was always in sight. He didn't know if it was part of his lucid dream or reality when Reborn would seemingly pat his head. Attachment was not meant for a Mafia Boss, nor a hitman.

"I'll stay for a few more years." Reborn had announced when Tsuna got slightly better. "It seems that Dame-Tsuna is still incapable of keeping himself healthy. That is unbefitting for a Mafia Boss."

Tsuna had cried in his room.

He is twenty-five.

Reborn is standing in his office, once more talking about the new season of Armani suits. Tsuna still hasn't fully comprehend Reborn's weird obsession with them.

"Dame-Tsuna, you'll rot if you sit behind the table for too long."

And so, Tsuna decides to bring his sarcastic, annoying, sadistic, demonic Spartan (and surprisingly whiny) of a tutor down the shopping streets of Italy. They walk side by side, sometimes Reborn still kicking him or pulling out a Leon gun.

And until the day when either one of them leaves, Tsuna will slowly relish and treasure his moments with the adult hitman.

* * *

 **Hope you liked it. And yes, Reborn is a late bloomer haha.**


End file.
